Method of producing rotors



1927' c. E. JOHNSON METHOD OF PRODUCING ROTORS Original File uly 8. 1924I. N R ..5 w w M 1 fl FmF A z a an x 3 .nZ/J 0 .9. f w 3 3 I 50illustrative Patented Aus- 1 1 I UNITED TATES' PATENT oFF 1,639,456 ICE.

uni-non or rnoncome neurons.

. I I v i Original apphoation fi-Ied'J'uly 8, 1924, Serial No. 724,800.Divided and this application filed April 27 1925. Serial No; 26,110.

This invention relates to a method. of making electrical apparatus'andrelates particularly to a method of making rotors for induction motorswhich ordinarily comprises 5 astator and a rotor. A rotor of thesquirrel-cage type comprises punchings; having holes therein, throughwhich holes conductor bars are extended. On each end of 12 these barsare secured end rings. The ends of the conductor bars are generallyturned down to a reduced diameter and extended through holes provided'in the the bars and sweated' to the ring to provides. good electricalcontact therebetween.

disadvantage in' this method is that considerable time is taken, first,m the ma bars and rings chme'work on the conductor and, secondly. in theinstallation of the .bars

and rings. It is also found that the bars tend'to work loose in therings, thus producing adefective rotor.

Ears

It is an object of this in'vention'to videa method whereby the conductorand the end rings may be cast integral, and in place, thus producingaqsuperior rotor. :It is alsonn object of the inventlon to provide a ypy. fore, since chining. A further object of this 1nvent1on is theprovision casting may be made.-

A special object is the provision of a meth-v 0d of producing a castingsubstantially free from blow holes.

My improved method of by casting may be it requires substantially nomadrawing and hereinafter described, and described and claimed in myco-pending application "entitled A paratus' for lproducingrotors, SerialNo. 'l24,800, filed uly 8 1924, of which 45 the present application is adiv1sion.

Additional objects of the invention and the advantages thereof. will bemade evident hereinafteix. v a

, Referring to'the; drawings which are for .P P y,- Fig. 1 is averticalsection through a'mold ,andassociatedapparatus. j 1 Fig.2 is a plan'view of Fig. -1 p and rings, being subsequently riveted over method bywhich a rotorL-of this 1 bemade much cheaper'than -be-,

i a method wherebyfasound 'rotor.

producing rotors practiced in connect] on 0 with the mold shown im theFig. 3 is a section taken g on a plane as indicated by the line 3--3 ofFig. .1. 1g. 4 is a section through a rotor having the conductorbars andrings castin a laminated core.

In practisingmyimproved method, I may provide a mold 11 which consistsof a body having a cylindrical wall 13. The inner face 14 of the wall 13provided a cylindrical portion 15 and a conical portion 16, whichconverges at the lower end thereof, these portions 15 and 16 beingseparated by an annular ledge 17. A body ring 20 is secured in the"'body12so as to rest on the bottom 21 thereof. The outer face 22 of the ring20 is conical so as to register with the conical face 16 of the body 12.The upper face 23 of the ring 20 extends in a plane .below the annularledge 17, as shown. Extending :upwardly from the in- 'ner edge of theface 23 is an annular lip .24, having. a conical outer face 26 whichtapers to the same extent as the face 16, but in an o positedirection... The upper face 28 of the ip 24,is arranged to extend intothe .same radial'plane as the annular ledge '17. The upper portion ofthe face 16 of the body 12, the upper face 23 of the ring 20,and theouter face 26 of the lip 24 cooperate to pro vide a lower annular. ringchannel 30. The ring channel 30, as clearly shown in Fig. 1, convergesand. is. narrower at the lower portionthereof. At intervals throughoutthe ring, wlngslots 32 are cut from the outer face 22 thereof. The innerface 33 of the wing slots-32 are arranged to extend in a plane aligningwith the-outer face 26 of the lip 24.

mandrel bar 35 is shown as being extended through an opening 36 in thebottom 21 so that the face 3-7 rests in the opening 36 and the shoulder38 rests against the annular face 39' pfovided-on the bottom 21, thehole 36 being concentric with the inner face 14 of. the body 12. Themandrel 35 extends upwardly and hasa cylindrica portion 40, a-taperedportion :11 and a threaded portion 42 e punchings 44 comprise the coreof the rotor. Q

unchings44 are assembled in the body as shown. The lowermost unchlng 45.18, arranged to rest on the annuar ledge 17 andthe upper face .28 ofthe11p 24. The 10 outside diameter of the punehings 44 15 of cap providesan and the face 28 of the the same diameter as the face 14 and theinside diameter 46- of the punchings 44 is of the same diameter as thecylindrical portion 40 of the mandrel Because of this, it will be seenthat the punchings 44 will be very accurately aligned when placed in thebody 12. The punchings 44 are provided with a plurality of holes 48which are also aligned when placed in the bod A cap 50 having an outercylindrical face 51 is then positioned so that this face 51 extends intothe upper end of the casting of the body 12 and so-thatan annular ledge52, provided between the face 51 and the conical inner face 53, willrest on the uppermost of the punchings 44. The conical face 53 extendsupwardly and meets with an annular and'radial face 54, provided by thecap 50. A cap ring 55 which is substantially identical with the bodyring 20 is then placed so that the upper edge 56 thereof rests againstthe face 54 and that the conical outer face 57 rests against the'face 53of the cap 50. The lower face 59 rests in a plane above the ledge52, asshown in Fig. 1. Extending downwardly from the inner edge of the lowerface 59 is an annular lip 60, which has an outer conical face 61 whichtapers to the same extent as does the conical face 53 of the body 50,but extends in an opposite direction thereto. The lower face 62 of thislip terminates in the same plane with the ledge 52. The ring 55 is alsoprovided with wing slots 54 which are cut from the outer face 57 andhave the face 65 thereof cut conical to align with the conical face 61of f the lip 60. The lower edge of the face 53 of the body 50, the lowerface 59 of the ring 55, and the outer face 61 of the lip (30 cooperateto provide an upper annular ring; channel 67. From comparisom'it willbeseen that the ring channels 30 and 67 are identical in shape, but ininverted relationship, and that the wing slots 32 and 64 are alsoidentical in shape, but inverted. The

opening 70 which converges at the upper end thereof. The inner face v71of the ring 55extends in a plane parallel to the face of the opening 70,as shown. Vents or risers 7 2 may be extended upwardly through the cap50 from the upper ends of each of the slots 64, as shown, these risers.72 being tapered upwardly.

A yoke 73 may then be positioned so that the pin 42 extends through ahole 7 4 thereof, and so that the legs 75 rest against the upper face 76of the cap 50. A suitable handled nut 77 is then screwed onto thethreaded portion 42 of the mandrel 35 and tightened in such a manner asto force the cap 50 downwardly so that the punchings 44 are verysecurely clamped between the ledge 17 body 12 and the ledge 52 and theface 62 of the cap 50.

After the punchings or core has been being poured through placed in themold and securely tightened as just described, the mold may then beplaced in a suitable preheating furnace and preheated and poured throughthe central opening 70 with a high grade of pure aluminum metal whichhas previously been melted. The metal entering the opening 70 passesthrough the passages 80 provided in the lip 60 and flows downwardlythrough the openings 48 of the punchings 44 into the lower ring channel30 and into the lower wing slots 32. After pouring the mold full, as themetal cools slightly and shrinks, it may be followed up with a littlemore metal, the opening 70, to compensate for the shrinkage. Any gaswhich forms in the mold 11 may pass out through the risers 72. When thejob is completed, it is allowed to cool in a suitable manner.

My experience has proved that the entire operation is very sensitive andthat certain regulations must be faithfully carried out. For example, ifthe molds are too cold, when the metal 'is poured, it will be found thatthe rings when taken out of the mold are usually cracked or checked,which proves that the degree of preheating of the molds, the propertemperature of the metal when poured and the rate of cooling must bevery closely controlled. Through experience have found that it isdesirable to preheat the mold to a temperature of between 775 degreesand 825 Fahrenheit. This is a temperature just below the red point. Ihave also found that the success of the process depends very largelyupon the proper tem- 'perature of the aluminum. 1 have found that if thealuminum is heated to a temper ature of between 1475 degrees and 1500degrees Fahrenheit, favorable results may ,be obtained. It is alsoextremely important that the job be cooled in proper manner. The jobshould be allowed to cool very slowly and gradually so that theconductor bar portions and the end ring portions may cool substantiallythe same. It has been found empirically that if the metal cools toorapidly, the end rings will cool off faster than theconductor bars andwill contract in such a manner that the metal is very likely to crack.

It is very desirable to place the mold upon a suitable vibrator orshaker 81 (Fig. 1) during and immediately after the pouring of the metalso that the gases may be thoroughly released from the mold and blowholes thereby substantially obviated.

One very important feature of my invention is that I provide a largecavity 70 in the cap of the mold above the rotor laminations. When themolten metal is poured, a large body of molten metal is formed in thelower part ofthis cavity, as indicated at 85 in Fig. 1. This body ofmetal in the 40 rigidly together by the integral bars 100' rotor; andshaking said mold d dicatedabove and in the following claims. said-molddcavity 70 is of such a size that it remains for a period thereafterandcooling the? 65 molten after the metal which has passed poured metalslowly an gradually.

into the mold has cooled. Therefore, as 2. he method of making, rotors,said the metal which eventually forms the conmethod comprising:preheating a mold andducting member of the rotor cools and a rotor coreto a temperature between 700 shrinkage takes place, additional metalunand 1000 degrees Fahrenheit; ouring T der the pressure due to the headof metal molten metal into ,the mold and t e core in the cavity, 70 willbe fed into the mold therein. at a temperature between 1400 and from,thebody of metal in the cavity 70, 1700 degrees Fahrenheit; shaking themold thus insuring a. homogeneous casting. This while the .metal isbeing poured'and for a P is especially important when castingalumiperiod thereafter; and cooling the poured num or an aluminum alloywhich has a high metal slowly and gradually. shrinkage factor, as suchalloys tend to 3. The method of making rotors, said shrink to such adegree as to leave large method comprising: preheating a mold and 1cayities in castings produced in the ordinary a rotor 'core to atemperature between 700 manner. I 1 and 1000 .degrees Fahrenheit;pouring After proper cooling, the rotor is removed molten aluminum intothe mold and the from the mold, this being done by removing core thereinat a temperature between" 1400 the nut 77, the yoke 73 and the cap 50.The and 1700 degrees Fahrenheit; shaking the metal may fill the mold 11,as indicated at 'mold while the aluminum is being. poured r the cap maybeeasily removed, however, and fora period thereafter; and cooling thedue to the draft which is provided onall poured aluminum slowly andgradually. the surfaces. The mandrel may 'then be 4. The "steps in themethod of making removed and the rotor removed from the rotors, whichconsist in: preheating a'mold body in a suitable manner. The finishedand a rotor core; pouring molten metal into product is shown in Fig. 4,the short pins the mold and the core therein; and shaking m 8 which mayfill the lower endof the risers the mold while the metal is being pouredbeing removed, and the central body 88 and for a period thereafter beingremoved by a separation from the 5. A method for producing rotors Whichrings at 89 at the outer edge of the passages comprises: placing punchiny mspection of Fig. 4; it will be seen pour ng a melted metal into saidmold td are provided integral. the rings 101 having said rotor; andshaking said mold during integral wings 102 which are for the purthecooling of 'said metal. 4 pose of creating a circulation of air when 6.A method for producing rotors which rotated, for ventilation. comprises:placing. punchings in a mold; 9 It will be recognized that owing to thecompressing said punchings together, pourfact that the punchings areforcibly clamped ing a melted metal into said mold to p together by thecasting, they will be held vide conductor bars and end rings forsaiduring the and rings 101. I cooling ofsaid metal. It will also be seenthat by casting the 7. A method for producing rotors which bars andrings'as described in a mold of this comprises: placing punchings in amold; character, a smooth and accurate job will preheating said mold;pouring a melted be produced which will require no 'machinmetal intosaid mold to provideconductor.

.1ng.. V ars and end rings for said rotor; and Although I have hereindescribed one shaking said mold during the cooling of complete.embodiment of my invention, it said metal; I will be understood thatvarious features 8. A method for producing rotors which 50 thereof mightbe independently employed comprises? placing punchings in a mold; andalso that various modifications might be compressing said punchingstogether; pres madeby those skilled in t e art, without eating saidmold; pouring a meltedmetal the slightest departure from the spirit andinto said mold to provide conductor bars scope of my nvention, as thesame is in' and end rin s for said rotor; and shaking I uring thecooling of said metal. 7 1 h1 s apphcation 1s a division of my 3P, 9. Amethod of forming rotors comprispticatlon Serial No. 724,800, filed July8, ing: preheating a mbld and core; pouring 1924. molten metal into saidmold; and forming I claim as my invention: a body of molten metal abovesaid core 1. The method of making rotors, said said bod beingsufiiciently. large so that method comprising; preheating amold and illcool first for a rotor core; pouring molten metal into the feedingmolten metal mto said mold asmold and the core therein; shaking the saidmetal in said mold cools.

9f forming rotors com- 4 nesaazse prising: preheating a mold and core;poura rotor core; pouring molten metal into the 1 ing molten metal intosaid mold; forming mold and the core therein; shaking sai a large bodyof molten metal above said mold for a period after said metal has beencore for feeding molten metal into said poured; and .cooling the pouredmetal mold as said metal in said mold cools; and slowly and gradually.

shaking said mold while it contains molten In testimony whereof, I havehereunto 15 metal. set my hand at Los Angeles, California,

11. The method. of making rotors, said this 20th day of Aglil, 1925.

method comprising: preheating a mold and BL E. J OHNSON;

